Magnet System Design and Optimization for a Novel Plasmoid Magnetic Reconnection Thruster Prototype

Abstract

The Plasmoid Magnetic Reconnection Thruster (PMRT) was proposed as a novel thruster concept based on the plasmoid ejection driven by magnetic reconnection. Stemming from fast magnetic reconnection studies conducted on the National Spherical Torus Experiment (NSTX), a PMRT prototype is under development at Princeton Plasma Physics Laboratory (PPPL), aiming to generate thrust through repeatedly creating plasmoids, enabled by helicity injection under a prescribed magnetic field. This static magnetic field is produced by a magnet system that serves as a core component of the plasmoid thruster and is essential to the occurrence of magnetic reconnection and the generation of plasmoids. This study focuses on the engineering design and optimization of the water-cooled copper magnet system to produce the prescribed static magnetic field with the target spatial distribution required by the PMRT. The design process begins with the target magnetic flux distribution derived from magnetohydrodynamic (MHD) simulation. Linear programming is employed to identify the optimal current distribution that minimizes the total conductor volume and reproduces the target magnetic field. A parametric sweep further refines the magnet configuration and determines the geometric parameters of the magnets. The final magnet design is validated through MHD simulation, ensuring plasmoid generation and completing a closed-loop engineering design process. In addition, the study addresses the integration of the magnets into the thruster prototype and confirms the structural integrity of the magnet system under operational conditions. This comprehensive approach delivers an economical and efficient design for the thruster’s core component, establishing a foundation for the development of a new cost-effective and robust plasma propulsion technology.